OTHR is a well established and economical, long-range, wide-area surveillance sensor technology. OTHR propagates high-frequency (HF) energy via the ionosphere to detect targets at distances of roughly 400 to 2,000 nautical miles (nmi) from the radar, within azimuthal sectors up to 90° wide. Operational OTHRs have been deployed at various locations in the United States and Australia for target detection applications, and the underlying technology is described in the literature of the art, for example, in J. M. Headrick and M. I. Skolnik, “Over-the-Horizon Radar in the HF Band,” Proc. IEEE, vol. 62, no. 6, pp. 664-673, 1974; T. W. Washburn, L. E. Sweeney, Jr., J. R. Barnum, and W. B. Zavoli, “Development of HF Skywave Radar for Remote Sensing Applications,” in AGARD Conf. Proc. No. 263, Special Topics in HF Propagation, V. J. Coyne, Ed. London, England: Tech. Editing and Reproductions, 1979, Ch. 32.; and James R. Barnum, “Ship Detection with High-Resolution HF Skywave Radar,” IEEE Jour. Oceanic Engineering., Vol. OE-11, No. 2, pp. 196-209, April 1986.
Current OTHRs deal separately with targets found in different target classes, where the target classes are defined by differing speeds and accelerations. The development of OTHR, directed at one new target class after another, has spawned unique methods for radar operation and signal processing to achieve optimal results for each target class. For example, the radar system is configured with short dwell periods for fast targets. Conversely, the radar system is configured with long dwell periods for slow targets that compete with stochastic earth clutter. Although the target application or “mode” can be switched rapidly, a deployment scenario involving detection of slow targets can preclude detection of faster targets, and vice versa. Moreover, some medium speed target detection modes have a target refresh rate that is too slow to acquire and identify high speed, high acceleration targets.
The OTHR development community has long recognized the limitation imposed by differing radar requirements for each target class. The solution of mode switching described above results in reduced capability. Another proposed solution to utilize multiple radar systems can be prohibitively expensive.
What is needed is a method and system to enable simultaneous detection and tracking of targets in multiple target classes by a single OTHR installation.